Optical sighting apparatus



Feb. 13, 1940. 2,190,569

c. D. MACG'ILL OPTICAL SIGHTIIIG' APPARATUS Filed Nv."21, 1958 2sheets-sheet 1 Fig. 1.

CHARLIE. 5 Qn). R YMPLE MMM.

Marl

Feb. 13, 1940.

c. DQ MAcGlLl. v 2,190,569

OPTICAL SIGHTNG APPARATUS Filed Nv. 21, 1938 2 sheets-'sheet 2 Fig. 3.

QHARL'EMSALRSME MM5 .H. /3 W! Y M "7. dfn) n 1'.. as the windscreen ofan aeroplane, which also 'rr-ica OPTKCL SHGHTING APPARATUS CharlesDalrymple Macglll, Annieslandflasgow, Scotland, assignor to Barr andStroud, Limite esiand, Glasgow, Scotland Application November 21, 1938,Serial No. 241,702- I in Great Britain December. 1, 1937 rename.

This invention refers to optical sighting apparatus of the type in whichthe target is viewed by the observer through a transparent screen such 5serves as a reector for presenting to the observer a reference image inthe line of sight to the target, the principal object of the inventionbeing to provide a sight of the transparent reecting screen type whichwill operate as a range estimam tor, or for the estimation of baselength of target, apart of the images being variable in accordance ggangle subtended by the target base, or course of with variation in thedistance apart of the focal target. plane marmngs. i According to thisinvention, provision is made Variation oi. the distance apart oi: thereferi. for setting two reference marks or points constiencemarks iseected by members which are rell' 15 tuted by optical images(hereinafter termed atively movable, for example relatively rotatable,3g )i marks) at Varying distances apart in the field or relativelymovable with a rectilinear motion.

oil view in which the target is seen, so that the Thus, in one example,at or approximately at the marks define the angle subtended at theobfocal plane O Sighting HDPE-fetus f the transservers eye by the targetbase, as indicated by the parent reecting screen type, a. firstgraticule has zo observer obtaining coincidence of the target basetransparent markings 011 en Dpaque background with the gap between thereference marks, the and a second graticule, movable relative thereto,apparatus being calibrated so as then to give has Opaque markings fOrmesme fr0 e greater 0r measurement of the subtended angle, range, orless extent the transparent markings, to produce length of target base,as may be required, dependvariation in the distance apart 'of the imageg ine on the data used in setting. irom the last of marks.

these, course of target can be estimated, as here- One example 0fCODSI'IICUOD Will HOW be deinafter explained. scribed with reference tothe acompanying draw- In carrying the invention into practice, meansings, in which: maybe provided for varying the distance apart Figure 1is a diaslemmetie Side View 0f the 30 ofthe reference marks bytheapplication diiersight.

` entially of movement corresponding with two of Figure 2 is a side viewof the collimator system the three factors, viz., range, vlength oftarget of the sight in section on the optical axis, base, and subtendedangle, and hence to obtain Figures 3, and 5 are plan views 0f deteil.the value of the third factor. Thus, if the base and 3'; length isknown, then setting of the reference Maures 6 and 7 are fragmentaryviews corre- S marks by the dierential application of move spending withFigure 2. ment corresponding with base length and the The apparatusShGWn in Figure 1 wmpses a further movement necessary to eiectcoincidence transparent reeetns Screen A and 8' olllimetor of the basewith the gap between the marks gives B. for producing e Virtuelreference image in the 40 a measure of range atthe moment ofobservation; observer's line of sight, which image in 'conse- 40similarly, i! the range is known, a measure of the quence appears at aniniinite distance to the eye,

i nase length can be obtained. Further. the magand apparently more orless coincident with the pitude ofthe angle subtended by the target istarget, so eliminating parallax eects. The eye represented by thedierence of the two move#- of the observer is indicated at C, observingthe ments applied in setting the reference marks. f target directlythrough the screen Aand also ob- 45 In addition, if the observed baselength does not serving the reference image.

agree with the known base length it may be in- The collimator B, seeFigure 2, comprises acasferred that the target is lying vat an angle'and ing 2,a lamp 3 at the lower end of the casing, a the value of thisangle and. hence, the 'course of collimator lens system t at the upperpart of the the target, can be estimated from the relacasing 2. a fixedgreticule 5, and a gretiule 5 10- gg Y Vtionship between the observedbase length and tatable about the axis of the collimator and situtheknown base length. ated face to face with the graticule 5, their ad- Ina further application, if the marks are set jacent faces beingsubstantially in the focal plane by movement corresponding with baselength and of the system, both graticule plates being of glass, 5gmovement corresponding with selected range, preferably ofaheat-resisting quality. The graticule 6 is carried by an annularmounting I which has two short diametrically opposed spindles projectingfrom it through slots in the casing 2, each spindle 8 having at itsouter end a pinion wheel S. Two annular operating heads I8 and I2 extendround the outside of the casing 2, about the axis of which they canrotate, each head having a ring of teeth to engage with the pinionwheels 9, one on the upper side and the other on the under side of thepinion wheels Q. This arrangement constitutes a dierential gear wherebyrotational movement which is the resultant of the rotational movement ofthe two heads I0 and I2 can be applied to the mounting 'l and thus tothe graticule 6. The heads i0 and I2 are set in accordance with scalesIBB and I2 suitably graduated to correspond with target base and range,the scales being, say, of logarithmic character and being, for example.on the collimator casing 2 alongside the heads i@ and I2.

- Referring now to Figures 3, 4 and`5, Figure 3 shows the lower face ofthe graticule bearing two separated diametrical line marks I3, and anyother marking that may be found desirable for sighting purposes, such asa circular mark Iii, these marks being transparent portions on an opaquebackground. To co-act with the marks I3 of graticule 5, the upper faceof the graticule 6 has opaque masking wings on a transparent background,see Figure 4. Figure 5 is a plan view showing the graticule 5 inposition above the graticule 6. In order that the transparent circularmark I4 should always appear complete, there are transparent arcs I6 inthe masking ,wings l5.

plane, directly through the screen A, and knowing its wing span, orother dimension which is to be the base of observation, and the range towhich it is desired to close before opening fire, he turns one of therings, say the ring i9, to correspond with the target base factor andturns the ring I2 to correspond with the range factor. The effect ofthis is to cause relative rotation of the graticules 5 and 6 with theresult that the masking wings I5 of the lower graticule mask the linesd3 of the upper graticuie to an extent corresponding with these twofactors, so that there appears in the line of sight a luminous image ofthe two lines I3, or of portions of these lines, separated by a distancewhich corresponds with the target base and the selected range, and thusthe inner extremities of the image lines deiine the angle subtended bythe target at the selected range. The target is seen between the imagelines and when the base coincides with the extremities of the imagelines, the target is at the selected range.

The relative movement of the heads `Iii and I2 is a measure of subtendedangle, and values oi subtended angle can be indicated, if desired, byproviding an index on one of the heads and an additional scale,graduated in angular values, on the other head. Such an arrangement isshown in Figures 6 and rI which are, respectively, a vertical sectionand a sectional plan of the left hand lower part of the apparatus shownin' Figure 2. On the upper face of the lower head I2 there is a scaleI'I, with which a pointer I8 projecting down from the head I0co-operates.

The graticules 5 and 6 may be made by etching the surfaces of the glassplates where they are to be opaque and coating the etched parts with anopaque heat-resisting substance.

I claim: l 1.; Optical sighting apparatus oi the transpar ent reiiectingscreen type, i. e. having a transparent screen through which the targetunder observation is viewed by the observer and which also serves as areflector for presenting to the observer a reference image in the line.of sight to the target, the apparatus comprising a colli: mating lightprojecting system having at or near its focal plane reference markingswhich are variable in their distance apart and virtual images of whichare produced in the observers line of sight by reflection at the screen,setting mecha- -nism for varying the distance apart of said referencemarkings and thus varying the distance apart of their images in thefield of view to deiine the angle subtended at the observers eye by thetarget base, as indicated by the observer obtaining coincidence of thetarget base with the gap between the reference images, and scale .meansassociated with the setting mechanism enabling movement of known valuecorresponding with range of target or base length of target or both, tobe imparted to the reference mark sety ting mechanism inA defining thesubtended angle, and also serving to give readings of either of thesevalues which may be unknown.

2. Optical sighting apparatus of the transparent reflecting screen type,i. e. having a transparent screen through which the target underobservation is viewed by the observer and which also serves as areflector for presenting to the observer a reference image in the lineof sight to the target, the apparatus comprising a collimating lightprojecting system having at or near its focal plane reference markingswhich are varia-- ble in their distance apart and virtual images oiwhich are produced in the observers line of sight by reection at thescreen, setting mechanism for varying the distance apart of .saidreference markings and thus varying the distance apart of their imagesin the field of view to denne the angle subtended at the observers eyeby the target base, as indicated by the observer obtaining co' tanceapart of the reference images, for the purpose set forth.

3. Optical sighting apparatus of the transparent reflecting screen type,i. e. having a transparent screen through' which the target underobservation is viewed by the observer and which also serves as a reectorfor presenting to the observer a reference image in the line of sight tothe target, the apparatus comprising a collimating light projectingsystem having at or near its focal plane a first graticule withtransparent markfings on an opaque background and a second graticulemovable relative thereto and having opaque markings for masking to agreater or less extent the transparent markings, virtual images of whichtransparent markings are produced in the observers line of sight byreflection at the screen, said images being variable in their distanceapart by relative movementI of the graticules to denne the anglesubtended at the observers eye by the target base, as indicated by theobserver obtaining coincidence of the target base with the gap bewe'enthe reference images, setting mechanism for effecting relative movementof the graticules and thus varying the distance apart of the referenceimages, and scale means associated with the setting mechanism enablingmovement of known value corresponding with range of target or baselength of target, or both, to be imparted to the reference mark settingmechanism in dening the subtended angle, and also serving to givereadings of either of these values which may be unknown.

4. Optical sighting apparatus of the transparent reflecting screen type,i. e. having a transpar- 'ent screen through which the target underobservation is viewed by the observer and which also serves as areflector for presenting to the observer a reference image inthe line ofsight to the target, the apparatus comprising a colllmating lightprojecting system having at or near its focal plane a iirst graticulewith transparent markings on an opaque background and a second graticulemovable relative thereto and having opaque markings for masking to agreater or less extentthe transparent markings, virtual images of whichtrans- 'parent markings are produced in the observers line of sight byreection at the screen, the reference images being variable in theirdistance apart by relative movement of the graticules to define theangle subtended at the observers eye by the target base, as indicated bythe observer obtainingcoincidence of the target base with the gapbetween the reference images, setting mechanism for effecting relativemovement of the graticules andVv thus varying the distance apart of thereerence images, a scale of range values, a scale of target base lengthvalues, means operating in .conjunction with the scale of range valuesfor applying movement to the reference mark Settim;

mechanism, and means operating in conjunction with the scale of targetbase length values for applying movement to said setting mechanism, thesetting mechanism including dierential gearing for combining themovement applied by said two operating means, and for applying it toeect relative movement of the graticules to vary the distance apart ofthe reference images, for.

the purpose set forth.

5. Optical sighting apparatus of the transparent reiiecting screen type,i. e. havinga transparent screen through which the target underobservation is viewed by the observer and which also serves as areiiector for presenting to the observer a reference image in the lineof sight to the target, the apparatus comprising a collimating lenssystem, a lamp for projecting light through the collimating lens system,at or near the focal plane of the lens system a iirst graticule havingtransparent markings on an opaque background and a second graticulerotatable relative thereto provided with opaque markings for masking toa Agreater or less extent the transparent markings, virtual images ofwhich transparent markings are produced in the observers line of sightby reiiection at the screen, said images being variable in theirdistance apart to define the angle subtended at the observers eye by thetarget base, `as indicated by the observer obtaining coincidence oi thetarget base with the gap between the reference images, a scale of rangevalues, a scale of target base length values, a rotatable operating headin conjunction with the scale of range values for applying movementcorresponding with range value, a rotatable operating head inconjunction with the scale of target base length values for applyingmovement corresponding with target base length value, and differentialgearing for combining the movement applied by the two operating headsand applying it to eiect relative rotation of the graticules to vary thedistance apart of l@ the reference images, for the purpose set forth.

6. Optical sighting apparatus of the transparent reflecting screen type,i. e. having a transparent screen through which the target underobservation is viewed by the observer and which l5 also serves as areiiector for presenting to the observer a reference image in the lineof sight to the targ'et, the apparatus comprising a collimating lightprojecting system having at or near its focal plane a first graticulewith transparent marmngs @9 on an opaque background and a secondgraticule movable relative thereto and having opaque markings formasking to a greater or less extent the transparent markings, virtualimages of whichA transparent markings are produced in the observers lineof sight by reection at the screen, theA reference images being variablein their distance apart by relative movement of the graticules to definethe angle subtended at the observers eye by the target base, asindicated by the ab observer obtaining coincidence of the target basewith the gap between the reference images, a Y logarithmic scale ofrange values, a" logarithmic scale of target base length values, meansoperating in conjunction with the scale of range values for applyingmovement to the reference mark setting mechanism, and means operating inconjunction with the s cale of target base length values for applyingmovement to said setting mechanism, the setting mechanism includingdiiierential gearing for combining the movement applied by said twooperating means and for applying it to eiect relative movement oi thegraticules to vary the distance apart of the reference images, for thepurpose set forth. '7. Optical sighting apparatus of thetransparentreflecting screen type, i. e. having a transparent screen through whichthe target under observation is viewed by the observer and which alsoserves as a reflector for presenting to the observer a reference imagein the line of sight to the target, the apparatus comprising a lightprojecting system, variable reference markings a virtual image of whichis produced in the observers line of sight by reiiection at the screenand by light from the light projecting system, the image constitutingtwo reference marks, setting mechanisni for varying said referencemarkings and thus varying the distance apart of the reference images inthe field of view to define the angle'" subtended at the observers eyeby the target base, as indicated by the observer obtaining coincidenceoi-the target base with the gap between the reference images, and scalemeans associated with the setting mechanism enabling movement of knownvalue corresponding with range of target, or base length of target, orboth, to be imparted to the reference mark setting mechanism inderlining the subtended angle, and also serving to give readings ofeither of these values which may be unknown.

` CHARLES DALRYMPIE MACGIIL.

